Fiber glass has been utilized for many years in the preparation of polyester resin fiber glass reinforced articles. One of the more important systems utilized in preparing fiber glass reinforced articles is the spray-up process. In this process a spray gun and a fiber glass roving chopper are combined so that the polyester resin to be utilized and roving are sprayed simultaneously onto a mold from a spray gun which has built into it a chopper. Fiber glass utilized for these purposes is provided in the form of roving and should possess good wet-out characteristics. Thus, the application of a satisfactory forming size on the surface of the glass fiber utilized to prepare the fiber glass roving for this use is important in providing a fiber glass product which is compatible with the polyester resins utilized in the spray-up process industry. Thus the sized roving must be capable of readily mixing with the resins used in the spray gun type applicator and should possess good laydown characteristics when sprayed on a mold in the manner conventionally employed in the spray-up industry.